1. Field of the Invention
The present invention relates generally to the production of maize, and more specifically to inbred maize lines designated 4SQ601 and 4SQ602, to parts thereof, and to maize plants produced using the same.
2. Description of the Related Art
As further background, maize, often referred to in the United States as corn, has long been the subject of plant breeding. Maize can be bred by self-pollination and cross-pollination techniques, both of which are typically employed in plant breeding programs with the object of combining a set of desired traits in a single maize hybrid.
Maize plants which have been self-pollinated and selected for type for several generations become homozygous at almost all gene loci. Such maize plants produce a uniform population of true breeding progeny, often referred to as an inbred maize line. In turn, these inbred maize lines are used primarily in cross-pollination with other inbred maize lines, to produce hybrid maize seed for commercial sale.
In general, the development of a hybrid maize variety involves three steps. Plants from germplasm pools or breeding populations are first selected. The selected plants are then self-pollinated, or "selfed", for several generations and selected to produce a series of true-breeding inbred lines differing from one another. Finally, the inbred lines are crossed with other inbred lines to produce hybrid progeny, (F.sub.1).
It is known that during the maize inbreeding process, the vigor of the maize lines generally decreases. This vigor is then restored when two different inbred lines are crossed to produce the hybrid progeny (F.sub.1). Importantly, a hybrid between a defined pair of inbred lines will always be the same, due to the homozygosity and homogeneity of the inbred lines utilized. Thus, hybrid maize seed can be sold to the market which yields a reliable, reproducible maize plant.
One maize trait of interest is kernel oil content. Standard maize grain typically contains about 3 to 4% oil on a dry weight basis. Maize grain having an elevated oil concentration, referred to as "high oil maize", has a higher caloric content per unit weight and is thus particularly advantageous for use as animal feed, and for its reduced dusting during milling. Because more than half of the maize grain produced in the United States is used for animal feed, the use of high oil maize for feed is of substantial commercial interest. This is particularly so in view of the high caloric demands in feeding poultry (Gallus gallus domesticus), swine (Sus scrofa), and dairy cows (Bos taurus). As it is, broiler and swine diets regularly contain added oil. Further, the full potential of bovine growth hormone in dairy cows will be more readily exploited if caloric intake is increased beyond that encountered with regular maize rations. Similar advantages may be expected in swine treated with porcine growth hormone.
Despite the expected advantages of high oil maize hybrids, the commercialization of high oil maize has been slow in progressing. This may be due to the fact that in several prior studies, breeding for high oil content has reduced yield both of inbreds and of hybrids made using the inbreds. Thus, competitive high-oil hybrids have proven difficult to develop.
In light of this background, a need exists for an inbred maize line having an elevated oil content and good combining ability with elite lines to produce competitive high oil maize hybrids. The present invention is addressed to this need.